... determined and quantied To ll these gaps, residues Y3 31, R97 and E187 of Sfbgly50 were replaced through site-directed mutagenesis by phenylalanine (Y331F), methionine (R97M), lysine (R97K) and ... stability of the recombinant Sfbgly50 (n) was checked by incubating the enzyme in the same buers for an equal length of time and determining the remaining activity in the pH optimum Fig Inactivation of ... 97 and 3 31 side chains are conserved in the mutants R97M and Y331F, but the hydrogen bond-forming atoms have been removed In mutant E187D, the distance between the catalytic nucleophile and the...